Obstructive sleep apnea (OSA) is a common medical disorder that can be quite serious. It has been reported that approximately one in twenty-two Americans (about 12 million people) suffer from OSA, and many cases go undiagnosed. Chronic fatigue has long been recognized as the hallmark of OSA, but more recently, large clinical studies have shown a strong link between OSA and strokes, and consequently, death.
Obstructive sleep apnea is a condition in which the flow of air pauses or decreases during breathing while one is asleep because the airway has become narrowed, blocked, or floppy. (See FIG. 1A of published patent application US20140246025 A1 to Cragg et al., published Sep. 4, 2014, which is incorporated herein by reference, illustrating an airway during normal breathing, and FIG. 1B therein, illustrating the airway A during OSA.) A pause in breathing is called an apnea episode, while a decrease in airflow during breathing is called a hypopnea episode. Almost everyone has brief apnea or hypopnea episodes while they sleep. In OSA, however, apnea episodes occur more frequently and last longer than in the general population. OSA has become an increasingly costly medical condition in recent years, as the disorder is more prevalent in obese people, and obesity has become significantly more prevalent. Unfortunately, the currently available options for treating OSA are not ideal.
A person with OSA usually begins snoring heavily soon after falling asleep. Often the snoring gets louder. The snoring is then interrupted by a long silent period during which there is no breathing. This is followed by a loud snort and gasp, as the person attempts to breathe. This pattern repeats. Many people wake up unrefreshed in the morning and feel sleepy or drowsy throughout the day. This is called excessive daytime sleepiness (EDS). People with sleep apnea may act grumpy or irritable, be forgetful, fall asleep while working, reading, or watching TV, feel sleepy or even fall asleep while driving, or have hard-to-treat headaches. OSA sufferers may also experience depression that becomes worse, hyperactive behavior (especially in children), or leg swelling (if severe).
The most widely used therapy for OSA is Continuous Positive Airway Pressure (CPAP). As shown in FIG. 2 of US20140246025 A1 to Cragg et al., a CPAP system 10 typically consists of a mask 12a-12c fitting in or over the nose or nose and mouth, an air pressurizing console 14, and a tube 16 connecting the two (typically a six-foot long hose with a 20 mm diameter bore). CPAP works by pressurizing the upper airway throughout the breathing cycle, essentially inflating the airway to keep it open, and thus creating what is sometimes referred to as a “pneumatic splint.” This flow is set at a pressure that has been predetermined through medical testing to be appropriate to create a pneumatic splint in the user's airway. This prevents airway collapse and allows the user to breathe without obstruction. Because the masks 12a-12c typically leak air, CPAP systems have to provide an airflow rate of up to 200 liters per minute (approximate figure based on unpublished data). The high airflow rate is needed for multiple reasons. First, all the air needed for breathing must come through the hose. Second, conventional masks have an intended leak built in for the purpose of constant “CO2 washout.” Third, these systems achieve the required pressure by using a high airflow rate to generate a back-pressure at the mask end, where the air is leaking out. Unfortunately, this high flow rate makes breathing feel quite uncomfortable for many users, and it requires a relatively large, noisy pressurizing console 14. Additionally, the high required flow rates of CPAP often cause discomfort during exhalation due to increased resistance, as well as nasal dryness, dry mouth, ear pain, rhinitis, abdominal bloating and headaches.
The overwhelming shortcoming of CPAP is poor user compliance. Over half of all users who try CPAP stop using it. Users dislike the side effects mentioned above, as well as having to wear an uncomfortable, claustrophobic mask, being tethered to a pressurizing console, the noise of the console, traveling with a bulky device, and a loss of personal space in bed.
Many CPAP devices and alternatives to CPAP have been developed, but all have significant shortcomings. Less invasive attempts at OSA treatment, such as behavior modification, sleep positioning and removable splints to be worn in the mouth, rarely work. A number of different surgical approaches for treating OSA have also been tried, some of which are still in use. For example, Uvulopalatopharyngoplasty (UPPP) and Laser Assisted Uvula Palatoplasty (LAUP) are currently used. Surgical approaches, however, are often quite invasive and are not always effective at treating OSA.
One alternative approach to OSA treatment is to provide a pneumatic splint during the expiratory portion of the respiratory cycle, by producing a partial blockage in the nose or mouth, thus slowing the release of air during expiration, and increasing positive pressure in the airway. The simplest way to form an expiratory pneumatic splint, pursing the lips, has been shown to open the upper airway and to improve breathing in emphysema users. This type of maneuver is generically labeled Expiratory Positive Airway Pressure (EPAP).
Ventus Medical, Inc. (http://www.proventtherapy.com/ventus_medical) has developed a removable nasal EPAP device to produce such a pneumatic splint during exhalation (the Provent® Sleep Apnea Therapy). (See, for example the published patent application US20060150978 A1 to Doshi et al., published Jul. 13, 2006, which is incorporated herein by reference.) This device restricts exhalation by forcing expired air through several small orifices attached to the nose. This is labeled a Fixed Orifice Resistor (FOR). Shortcomings of this therapy are that 1) the fixed hole exhalation valve does not have a capped maximum pressure, 2) the pressure increases immediately upon exhalation and therefore makes it difficult to exhale, and 3) with no assistance of additional pressure from an external source, if the user has an apneic event, there is no ‘rescue pressure’—i.e., the flow supplied by the blower box 180. A further disadvantage is that the Provent® device or any FOR restricts expiratory airflow using a fixed hole for resistance. This leads to an uncomfortable spike in nasal pressure at the beginning of expiration, when airflow is highest, and a less efficacious decrease in nasal pressure at the end of expiration, when airflow is lowest. Another shortcoming of the Provent® device is that it produces the pneumatic splint only during exhalation—i.e., there is no increased pressure during inhalation.
In addition, the device is not effective in mouth breathers or users who become mouth breathers when resistance is added to the nasal passages. Thus, the Provent® device is useful only in moderate cases of OSA that do not convert to mouth breathing.
Although snoring is not as severe a condition as OSA, it does affect lives adversely. Snoring can adversely affect sleep quality and can make sleeping with a spouse or other partner difficult. Although many snoring therapies have been tried, including Breathe Right® Nasal Strips and more invasive approaches in more severe cases, no ideal solution has been found.
Therefore, it would be advantageous to have improved systems, devices and methods for treating OSA and snoring. Ideally, such systems, devices and methods would be less cumbersome than currently available CPAP systems, to improve user compliance. Also, ideally such systems, devices and methods would provide some of the advantages of an expiratory pneumatic splint. At least some of these objectives were met by the embodiments described in US20140246025 A1 to Cragg et al., previously incorporated herein by reference (herein sometimes referred to as “Cragg '025”).
Cragg '025 utilized a novel system of valves to allow inspiration of air supplied via the hose and also from inlets in the mask that take in room air. In various example embodiments, Cragg '025 provided variable resistance to expiratory air flow using a resistive mechanism other than infused external air that increases over the course of expiration, thus providing an easier, more comfortable start to expiration, while maintaining airway pressure toward the end of expiration (e.g., by decreasing resistance to expiratory flow when intranasal pressure reaches a threshold pressure and/or by gradually increasing resistance to expiratory air flow until intranasal pressure reaches the threshold pressure). Another improvement in various embodiments of Cragg '025 was that lower air flow rates were used (e.g., less than or equal to 20 L/min), while still supplying the desired therapeutic pressure (e.g., between about 4 cmH2O and 20 cmH2O), thus requiring less power and smaller device components than traditional CPAP and reducing side effects. Still another improvement of Cragg '025 was a less cumbersome, more form-fitting mask that reduced air leaks and was more comfortable to wear than prior CPAP masks, which eliminated the need for high flow rates because there was no need to compensate for air leaks. Accordingly, the devices described therein could be used in connection with a small diameter hose (e.g., having a diameter of less than or equal to about 15 mm), thus decreasing the bulkiness of the system.
While Cragg '025 was an important improvement over the state of the art, it required and relied upon a special system of protruding valves that had to be pre-adjusted or set to suit each user. It would be advantageous to improve upon the system of Cragg '025 by making the system simpler and more compact in design, simpler to use, and more robust.